The purpose of this study is to gain more information about the step-by-step process that causes someone to develop type 1 diabetes. Scientists think that a person's own immune system, directed by genetic and environmental factors play a major role in its development. Participation involves a blood draw, a brief medical history questionnaire and measurements of height and weight. Some participants will be asked to return for annual follow-up visits for 10 years.

The goal of this project is to gain knowledge about the development of Type 1 diabetes (T1D), as T1D is one of the most common chronic diseases in children. There has been a rise in the number of cases diagnosed as well as a decrease in the age of diagnosis. This project aims to understand the disease progression as seen in the immune system and to define the genetic and environmental factors that affect inflammation and regulation, which could determine disease progression or nonprogression. Families that include a family member with T1D will be recruited, as well as unrelated, healthy controls as a comparison group.

Participants will have height and weight measured, complete a social & medical history questionnaire, and have blood drawn for analysis for HLA haplotype (a genetic sequence related to type 1 diabetes susceptibility)diabetes, blood glucose, immune system response, complete blood count, and autoantibody measurements. Some family members may return for follow-up visits for up to 10 years.

Inclusion Criteria (Families):

• Families where at least one first-degree family member has type 1 diabetes
• The diabetic proband in the family was diagnosed before the age of 39
• Family members must be at least 2 years old to participate

Exclusion Criteria (Families):

• Families with no history of type 1 diabetes
• Families with a history of diabetes that is not type 1 (LADA, MODY, type 2 etc.)

Inclusion Criteria (Controls):

• No family history of type 1 diabetes or other autoimmune conditions
• Age 2 or older

Exclusion Criteria (Controls):

• Personal or family history of autoimmune disease

Patients with T1D seen at clinics at the Children's Wisconsin (n~1500) and Froedtert Hospital (n~800) will be targeted. In families with a child proband, siblings will be asked to join the study. If the diabetic child has an aunt, uncle, or cousin with T1D, then siblings in that nuclear family will also be recruited. Adult proband families will include the adult affected by T1D and their children. Adult proband families must include children <17 years of age. If the adult proband has a sibling, niece, or nephew with T1D, siblings in that nuclear family will be recruited as well. The age-of-diagnosis criterion for the proband will be less than 39 years and insulin therapy started within 5 years of diagnosis.

Unidentified samples and data will be shared with other researchers.